Ship-propeller.



M. E. DAVIS.

SHIP PHOPELLER.

APPLICATION FILED JUNE 16, l9l6.

1,216,549. Patented Feb. 20, 1917.

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MATTHEWS E. DAVIS, OF NEW YORK, N. Y.

sHiP-PROPEL LER.

Specification of Letters Patent.

Patented Feb. 2o, iei'r.

Application filed June 1c, 1916. Serial No. 103,916.

To all Hill/OWL it may concern.

Be it known that I, MATTHEWS E. DAVIS, a citizen of the United States, residing at New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Ship- Propellers, of which the following is a specification.

This invention relates to improvements in steel or cast iron ship propellers and the protection of steel or iron hulls from electrolysis when provided with my improved propellers.

Steel or cast iron propellers are more desirable than bronze propellers or propellers made of special metals because they are cheaper and also because their blades are not so apt to be distorted by collisions with obstacles that commonly bend bronze and special metal blades. On the other hand, steel and cast iron propellers become, so pitted in the blade tip portions, especially in salt water, that new propellers are required about every two years and sometimes oftener. A theory of the cause of thepitting action accepted by some authorities is that oxygen is released from the air bub-j bles which form on the backing side of the propeller blades just aft of the forward edge toward the tips, and attacks the steel or cast iron. To avoid this destructive action, steel and cast iron propellers have been painted or covered with cement, but these methods do not give a satisfactory protection and resort has been had to detachably mounted blade tips permitting replacement of the eaten out or pitted tips, the zone of deterioration usually extending one-third of the length of the blade from the tips and being just back of the entering edge on the back of the blade. The best approved means of avoiding the damage to steel or cast iron propellers is to give up their use and use the more expensive bronze propellers even though the bladesvo-f bronze propellers 'are less stiff and more subject todeformation than steel or cast iron propellers. While I have referred to propellers of special'metal, I am not aware that any satisfactory substitute for steel, casti ron' and bronze has been found for approved use in the manufacture of ships propellers, especially. for salt waters.

My idea of an effective way of overcoming the expense and annoyance attendant on the use of steel and cast iron propellers is facture and durability faces of to coat them with copper or other metal which is highly resistant to the action of oxygen in salt water, or at any rate is highly resistant to the pitting action mentioned. But inasmuch as propellers of the class which is particularly within the object of my improvement are almost in variably used'in steel hulls, the copper or resultantly equivalent metal coating, if such metal'comprises copper, leads to a practical difficulty of the utmost importance, so that although my metallically coated steel or cast iron propellers are of themselves highly desirable from the viewpoints of low cost, stiffness and approximate non-deformability, yet they are considered of and by themselves, and simply as non-pitting metallically coated propellers, antagonistic in effect to steel or ironhull's, and would involve ultimate destructive damage thereto, because of electrolysis, if it were not that by my invention means are provided for efficiently nullifying the constantly existing electrolysis so'far as destructive action on the steel or iron hull is concerned. My problem therefore involves a reconcilement of antagonisms, and this I accomplished by the means described below. The electrolysis results from the proximity of the propeller when coated with copper or with a special metal containing copper, and of the steel or iron" hull in water, especially salt water, the copper, steel or iron and salt water setting up a strong electrolytic or galvanic current that is very rapidly destructive of a steel or iron hull. Moreover electrolysis or some similar destructive process is more and more encountered in the present times because of the use of Wireless telegraphy and the grounding of electric current leads in harbors, and the question of the protection of steel or iron hulls from such destructive agencies is one of large importance. Just how far, if at all, the GlGCtlOlYtlQOP gal vanic forces are increased by other currents alluded to, nobody knows -At any rate, if copper or a copper-containing metal is to be used to coat steel and cast iron propellers as is highly desirable for economy of manuof propeller blades, then it is essential that the electrolytic or galvanic action referred to be made negligible on steel or iron hulls equipped with so coated propellers.

Efficiency requires that the outward surthe propeller be smooth in order to slip smoothlylin waterand minimize skin friction, and myimproved propellers coated with copper or metal containing copper "have asmootlr skin or =outward surface which is durable; Considered by itself, my

new-steel or cast iron copper-coated propeller' is stiffer and cheaper than bronze pronot crack or'peel off, adds strength'to the of paint doesnot do, and slips better in water; Moreover mycopper coating lines the hub bore and'keyway and thus protects Y bore, also somu chof the steel shaft as is in the hub protecting the steel key that splinesfthe propeller'hub to the shaft. I form my coating by plating or other suitable coatingiprocess, of which 'several "are known, 5 w r V The Qaccompanymg drawing forming a 7 part hereofis a vertical central section of one form of a propeller andiits mounting in r [a steel or iron hull, and fully illustrates my invention as embodied in a built-up propeller. 'Thecored-out and thereby chambered -steel or ironi hub is interiorlyand also externally'coated, and the d'emountablesteel oriron bladesare alsorwholly coated in the formgshown. V

' In the drawing, 1 is a steel propeller shaft having ja sternen'd taper, 2 a bronze sleeve sh'runkfin place onlthe steel shaft, 3 a built up propeller hnbofjcast iron or steel forming a coreifor the coating or'incasem'ent of V plated mare the propeller blades of cast iron or-steel, 5 the copper or equivalently functioning coating or incasement, 6 an anhold the demountable blades tothehub, and

'nular recess in the forward end of'th'e hub for reception of; the sternward' end of the bronze sleeve, 7 a water-excluding gasket at the joint 7 'betweenstheopposed ends of said sleeve and hub, 8 the-clamp nut which holds the propeller inplaceon the shaftpin coepera tion with the key 9. 10 are taps which V 11' ;is a lignum vitae bearing which the 7 bronze sleeve ismounted, this lignum vitae f LN 1 bearing insulating the iron or steel hub from the bronze sleeve; 12 is a fair water which may be omitted if -preferred, and 13 V are zinc plates shown mounted in functional f proximity to the propeller. Some of these zinc 'pl'ates'are, on" the walls of" the propeller 'aperture,'and one of them'isindicated by dottedilines as applied to' 'the 'us ual hublike "portio 'nfof the propeller aperture where the qe pies er this-patent may he' obtai n ed propeller shaft passesiinto such aperture to hold the propeller in place. The zinc plates 13 function as protectors for the steel or iron hull against electrolytic action which severely attacks the zinc and leaves the hull comparatively safe from electrolysis. These zinc protector-plates are eaten in time and have to be'replaced at intervals.

The copper-containing metal is the best kind of metal now known to me for resisting'the pitting action. But any other pitting-resistingmetal which at the same time willact with another metal in proximity to a propeller insulated from an iron or steel hull for protection of such hull against electrolytic injury, I deem to be an equivalent of my preferred copper-containing metal'for all purposes; and it is to be observed that the coating which I have referred to for the propeller is not merely a thin skin, but is a deposit or coating or plating of substantial thickness whereby it adds to the strength of the propeller blades cross-sectionally. It also adds in a certain sense to the strength of the hub, but the hub is not. under such strains as are the propeller blades and it'is the strengthening of the steel or iron propeller blades by the metallic coating that is important. Obviously the propeller may be a built-up propeller such as herein shown, or a single-piece propeller in which the hub and blades are integral.

What I claim is:

The combination'of an iron or steel hull, with a steel propeller shaft having a fixed sleeve insulated from the hull; a propeller keyed to and also clamped endwise in place on the shaft; and a gasket between theop- I posed Walls of the sleeve and propeller hub; the propeller comprising an iron or steel propeller-shaped core and a copper-containing metal coating on its surfaces, and the hull being provided with removable zinc plates adjacent the propeller; the coppercontaining metal coating resisting pitting and preventing pitting of the coated profpeller core and of the portion of the shaft 'in the propeller hub bore; and the zinc plates in proximity to the propeller protecting the hull against electrolytic action; and the gasket excluding water from access to the shaft at the joint between the opposed walls of said sleeve'and propeller hub; and the said metallic coating increasing the strength of the blades cross-sectionally.

V In testimony whereof I have hereunto set my hand this 13th day of June, 1916.

a MATTHEWS E. DAVIS.

five cents each, by'aedressing the Commissioner of Patents. 'wasihington hfll 

